System is in a boot loop, receiving a bus error exception


Wed, 11/18/2009 - 18:25
Jun 18th, 2009

Core Issue

Bus error exceptions can be caused in these instances:

  • Loaded Cisco IOS  Software does not support installed hardware
  • Software failure
  • Mis-seated hardware
  • Hardware failure


Usually, a boot loop caused by a bus error exception is hardware related.

To resolve this issue, perform these steps:

  1. Verify that all network cards are supported by the Cisco IOS Software.  


    For minimum versions of Cisco IOS Software needed for the hardware, refer to Software Advisor.


  2. If you have a router that supports a boot image, such as the Cisco 7200 or 7500 series router, verify that the bootflash image supports the hardware installed.  

  3. The information contained in the bus error does not help to isolate the hardware. Therefore, it is important to remove and reinsert cards to find the problem hardware.  


    Perform these steps:

    1. For modular routers, remove the cards and reload the router. If the router boots without errors, add cards one at a time to discover the faulty module.      

    2. If removing the cards does not solve the problem, try reseating the system Flash and DRAM.      

    3. Replace the faulty hardware.

  4. Rarely, the bus error exception boot loop can be caused by a software fault.  


    If you notice the problem immediately after upgrading the Cisco IOS Software, perform the steps in the Software Failure section of Troubleshooting Bus Error Crashes.


When hardware replacement is indicated, choose from one of these options:

  • If you have a hardware support contract directly with Cisco for this part, use the RMA Service Order Tools to request a replacement part directly.  

  • For warranty service, contact the Cisco Technical Assistance Center (TAC) directly at 1-800-553-2447 or online using the TAC Service Request Tool.  

  • If your product is not covered by contract or warranty, contact your Cisco partner or reseller to request a replacement part for the hardware component that is causing the issue.

Error Messages and Warnings

*** System received a Bus Error exception ***



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